Jumbo-size screen image display apparatus that are set up in a ground such as a baseball field, a soccer ground and so on or a wall of a building and so on generally have relatively few pixels in which 320 pixels are arranged in the horizontal direction and 240 pixels are arranged in the vertical direction, for example. In such known jumbo-size screen image display apparatus, one pixel is comprised of a set of small/non-deflection CRTs (cathode-ray tubes) each including red (R), green (G), blue (B) fluorescent screens, one pixel is comprised of a set of LEDs (light-emitting diodes) each for emitting lights of red, green and blue or the like.
FIGS. 10 and 11 show the manner in which pixels are arranged in the conventional jumbo-size screen image display apparatus.
In FIGS. 10 and 11, one pixel is formed by arranging color elements 1 [1R, 1G, 1B] of elliptic red, green, blue LEDs at vertexes of a triangle. The manner in which the color elements 1R, 1G, 1B are arranged at vertexes of the triangle in this manner is referred to as a delta color element arrangement. To be more in detail, the manner in which color elements are arranged in FIG. 10 is called a lateral-delta color element arrangement and the manner in which color elements are arranged in FIG. 11 is called an inverse-delta color element arrangement. Further, in any of FIGS. 10 and 11, respective pixels are simply arranged in the longitudinal and horizontal directions. The manner in which pixels are simply arranged in the longitudinal and horizontal directions as described above is called a square arrangement.
There is also an increasing demand that the jumbo-size screen image display apparatus for use in a ground, an advertisement on the wall of building or the like exhibits a higher image quality. In particular, a high contrast at which a picture may become clear under high illuminance, a high resolution which enables an object image to be displayed as detailedly as possible or a small pixel pitch which may cope with a relatively small image is of great importance.
Then, since it is difficult to form a large screen integrally, it is customary that a large screen is formed by a combination of a plurality of small screens. In that case, however, it is unavoidable that an ineffective portion such as an attachment space, a thick portion of case and so on occurs in a joint of small screens. To solve this problem, elements of three colors are grouped, and a pixel pitch is provided by adding the ineffective portion to an effective portion. At that time, considering a uniformity of a screen, it is necessary that a pixel pitch within small screens and a pixel pitch between small screens become equal to each other. Also, since a finally-assembled screen is of oblong rectangle, small screens also are made rectangular. Therefore, when it is intended to obtain a small pixel pitch by using small elements for every color like the LED, generally, elements of three colors are arranged in a delta-fashion by grouping the ineffective portions and the pixels thereof are arranged in a square-arrangement fashion. In FIGS. 10 and 11, for example, one small screen (so-called unit cell) Pi, j, Pi+1, j or the like comprises 16 pixels formed of 4 pixels in the horizontal direction and 4 pixels in the vertical direction. Then, FIG. 10 shows that a pixel pitch is L1, and FIG. 11 shows that a pixel pitch is L2.
Further, in order to avoid lowering of a contrast by an external light, in FIGS. 10 and 11, each pixel includes eaves (louver) 2 provided on its upper portion as shown in FIG. 12. The louver 2 should preferably be sized so as not to narrow upper and lower visual field angles .theta.3, .theta.2. Therefore, the LED on the lower side of the delta layout, i.e. color element 1 (red color element IR in FIG. 10 or blue color element 1B in FIG. 11) is unable to completely interrupt external light. Thus, if there is an incident light of low angle, then such incident light is not interrupted by the louver 2, reached and then reflected on the screen, thereby resulting in a contrast being lowered. Moreover, if an angle looking at screen upward exceeds a design visual field angle (angle at which the louver 2 may not hide the LED element 1) .theta.4, then the LED color element 1 on the lower side of the delta layout is hidden by the upper louver 2 of the pixel beneath it. There is then the drawback that a color is changed. In this connection, by way of example, an external light incident angle .theta.1 is about 25.degree., the lower visual field angle .theta.2 is about 28.degree., the upper visual field angle .theta.3 is about 1.degree. and the design visual field angle .theta.4 is about 29.degree..
On the other hand, as shown in FIG. 9, there may be considered a jumbo-size screen image apparatus in which one pixel is formed by aligning in a line a red element 1R, a green element 1G and a blue element 1B, each of which is formed of an elliptic LED. To align the color elements 1 [1R, 1G, 1B] in a line in this way is called an in-line color element arrangement. Also in this case, since pixels are simply arranged in the longitudinal and horizontal directions, this arrangement is called a square arrangement. Although the color elements are not hidden by the louvers so that a color is not changed in the jumbo-screen image apparatus in which the pixels are arranged as described above, it is difficult to reduce a pixel pitch L3. Moreover, since the number of pixels per unit area is decreased, a brightness is lowered so that an image of high-definition may not be obtained. Also, when the color element is comprised of a CRT (cathode-ray tube), a degree at which a contrast is lowered by an external light at low incident angle is greater than a degree at which a contrast is lowered in the delta-arrangement.
Furthermore, there is known such an image display apparatus that an apparent horizontal resolution and an apparent vertical resolution are increased by an oblique arrangement in which a pixel is shifted at every row by a half pitch. However, when a large screen is formed of a combination of a plurality of small screens, it is difficult to maintain an ineffective portion. Therefore, the application of such known image display apparatus is limited to an integral-type liquid-crystal display apparatus.